Hi

When have  you passed your class twelfth and have you studied maths in your 10 + 2?

Now worries,

Eligibility criteria says that to be eligible  for JEE mains 2021 for BE or Btech you should be either appearing for 12th board exam or equivalent  in 2021 or should have passed it in 2020 or 2019 with Physics,  mathematics and anyone of Chemistry or Biology or Biotechnology or Technical Vocational Subject.

So, if you fulfill the above eligibility criteria then yes you can appear in JEE mains 2021 examination even if you're doin g Bsc biology

Also,

There is a small change in JEE Mains examination pattern , in your jee mains 2021 there will be 30 questions in each subject ,20 questions will be MCQs and rest 10 questions will be questions with numerical value as the answer , out of which only 5 questions are  to be attempted.

For detailed information go through

https://engineering.careers360.com/articles/jee-main-eligibility-criteria

Thankyou